Coverage Effects of the ACA's Medicaid Expansion on Adult Reproductive-Aged Women, Postpartum Mothers, and Mothers with Older Children.

Objectives: We estimate the effect of the Affordable Care Act's (ACA) Medicaid expansions on Medicaid coverage of reproductive-aged women at varying childbearing stages.

Methods: Using data from the American Community Survey (ACS) (n = 1,977,098) and a difference-in-differences approach, we compare Medicaid coverage among low-income adult women without children, postpartum mothers, and mothers of children older than one year in expansion states to non-expansion states, before and after the expansions.

Results: The ACA's Medicaid expansion increased Medicaid coverage among adult women with incomes between 101 and 200% of the federal poverty line (FPL) without children by 10.7 percentage points (54 percent, p < 0.01). Coverage of mothers with children older than one year increased by 9.5 percentage points (34 percent, p < 0.01). Coverage of mothers with infants rose by 7.9 percentage points (21 percent, p < 0.01).

Conclusions For Practice: Within the population of adult reproductive-aged women, we find a "fanning out" of effects from the ACA's Medicaid expansions. Childless women experience the largest gains in coverage while mothers of infants experience the smallest gains; mothers of children greater than one year old fall in the middle. These results are consistent with ACA gains being the smallest among the groups least targeted by the ACA, but also show substantial gains (one fifth) even among postpartum mothers.